This PR adds a new fork which disables EIP-1283. Internally it's called Petersburg,
but the genesis/config field is ConstantinopleFix.

The block numbers are:

    7280000 for Constantinople on Mainnet
    7280000 for ConstantinopleFix on Mainnet
    4939394 for ConstantinopleFix on Ropsten
    9999999 for ConstantinopleFix on Rinkeby (real number decided later)

This PR also defaults to using the same ConstantinopleFix number as whatever
Constantinople is set to. That is, it will default to mainnet behaviour if ConstantinopleFix
is not set.This means that for private networks which have already transitioned
to Constantinople, this PR will break the network unless ConstantinopleFix is
explicitly set!

params: fix golint warnings

Blockchain tests now include the "network" which determines the chain
config to use. Remove config matching based on test name and share the
name-to-config index with state tests.

Byzantium/Constantinople tests are still skipped because most of them
fail anyway.

Tests are now included as a submodule. This should make updating easier
and removes ~60MB of JSON data from the working copy.

State tests are replaced by General State Tests, which run the same test
with multiple fork configurations.

With the new test runner, consensus tests are run as subtests by walking
json files. Many hex issues have been fixed upstream since the last
update and most custom parsing code is replaced by existing JSON hex
types. Tests can now be marked as 'expected failures', ensuring that
fixes for those tests will trigger an update to test configuration. The
new test runner also supports parallel execution and the -short flag.

Two new tests are skipped because they're buggy. Making some newer
random state tests work required implementing the 'compressed return
value encoding'.

We used to have reporting of bad blocks, but it was disabled
before the Frontier release. We need it back because users
are usually unable to provide the full RLP data of a bad
block when it occurs.

A shortcoming of this particular implementation is that the
origin peer is not tracked for blocks received during eth/63
sync. No origin peer info is still better than no report at
all though.

Assuming the following scenario where a miner has 15% of all hashing
power and the ability to exert a moderate control over the network to
the point where if the attacker sees a message A, it can't stop A from
propagating, but what it **can** do is send a message B and ensure that
most nodes see B before A. The attacker can then selfish mine and
augment selfish mining strategy by giving his own blocks an advantage.

This change makes the time at which a block is received less relevant
and so the level of control an attacker has over the network no longer
makes a difference.

This change changes the current td algorithm `B_td > C_td` to the new
algorithm `B_td > C_td || B_td == C_td && rnd < 0.5`.

I forgot to update one instance of "go-ethereum" in commit 3f047be5.

All code outside of cmd/ is licensed as LGPL. The headers
now reflect this by calling the whole work "the go-ethereum library".